U.S. patent application number 13/691946 was filed with the patent office on 2014-06-05 for method and system of geophysical surveys in marine environments.
This patent application is currently assigned to PGS GEOPHYSICAL AS. The applicant listed for this patent is PGS GEOPHYSICAL AS. Invention is credited to Stig Rune Lennart TENGHAMN.
Application Number | 20140153362 13/691946 |
Document ID | / |
Family ID | 49918137 |
Filed Date | 2014-06-05 |
United States Patent
Application |
20140153362 |
Kind Code |
A1 |
TENGHAMN; Stig Rune
Lennart |
June 5, 2014 |
METHOD AND SYSTEM OF GEOPHYSICAL SURVEYS IN MARINE ENVIRONMENTS
Abstract
Geophysical surveys in marine environments. At least some of the
illustrative embodiments are methods including: attaching a first
sensor module to a sensor cable having an outer jacket, the first
sensor module electrically isolated from an electrical conductor
disposed within the outer jacket of the sensor cable; attaching a
second sensor module to the sensor cable, the second sensor module
electrically isolated from an electrical conductor disposed within
the outer jacket of the sensor cable; placing the sensor cable and
the sensor modules onto a sea floor; communicating with the sensor
modules by way of the electrical conductor disposed within the
outer jacket; collecting geophysical data by the first and second
sensor modules while the sensor cable is on the sea floor; and
downloading to a computer system geophysical data from the first
and second sensor modules.
Inventors: |
TENGHAMN; Stig Rune Lennart;
(Katy, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PGS GEOPHYSICAL AS |
Lysaker |
|
NO |
|
|
Assignee: |
PGS GEOPHYSICAL AS
Lysaker
NO
|
Family ID: |
49918137 |
Appl. No.: |
13/691946 |
Filed: |
December 3, 2012 |
Current U.S.
Class: |
367/20 |
Current CPC
Class: |
G01V 1/3808 20130101;
G01V 1/202 20130101; G01V 1/201 20130101; G01V 1/3852 20130101 |
Class at
Publication: |
367/20 |
International
Class: |
G01V 1/38 20060101
G01V001/38 |
Claims
1. A method comprising: attaching a first sensor module to a sensor
cable having an outer jacket, the first sensor module electrically
isolated from an electrical conductor disposed within the outer
jacket of the sensor cable; attaching a second sensor module to the
sensor cable, the second sensor module electrically isolated from
an electrical conductor disposed within the outer jacket of the
sensor cable; placing the sensor cable and the sensor modules onto
a sea floor; communicating with the sensor modules by way of the
electrical conductor disposed within the outer jacket; collecting
geophysical data by the first and second sensor modules while the
sensor cable is on the sea floor; and downloading to a computer
system geophysical data from the first and second sensor
modules.
2. The method as defined in claim 1 wherein attaching the first
sensor module further comprises connecting the first sensor module
such that at least a portion of the first sensor module abuts and
circumscribes the outer jacket.
3. The method of claim 1 wherein downloading further comprises
communicating at least a portion of the geophysical data to the
computer system by way of the electrical conductor while the sensor
cable is disposed on the sea floor.
4. The method of claim 3 wherein downloading further comprises:
retrieving the sensor cable from the sea floor; and downloading at
least a portion of the geophysical data from the first sensor
module through a communication port of the first sensor module; and
downloading at least a portion of the geophysical data from the
second sensor module through a communication port of the second
sensor module.
5. The method of claim 1 wherein downloading further comprises:
retrieving the sensor cable from the sea floor; and downloading
geophysical data from the first sensor module through a
communication port of the first sensor module; and downloading
geophysical data from the second sensor module through a
communication port of the second sensor module.
6. The method of claim 1 wherein attaching the first sensor module
further comprises attaching the first sensor module at a location
on the sensor cable where the outside diameter of the outer jacket
is uniform.
7. The method of claim 1 where attaching the first sensor module
further comprises attaching the first sensor module at a location
on the sensor cable where the outer jacket is continuous along an
axial length of the sensor cable.
8. The method of claim 1 wherein communicating further comprising
sending a command to begin recording geophysical data, the sending
at least in part over the electrical conductor.
9. The method of claim 1 wherein communicating further comprises
sending a time reference over the electrical conductor.
10. The method of claim 1 wherein the geophysical data comprises at
least one data type selected from the group consisting of: seismic
data, electromagnetic data, or any combination thereof.
11. A system comprising: a sensor cable comprising: an outer
jacket, the outer jacket defining an interior volume; and a first
electrical conductor disposed within the interior volume; a first
sensor module comprising: a coupling member configured to be
releasably coupled to the outer jacket of the sensor cable; a
sensor coupled to the coupling member; and a control circuit
communicatively coupled to the sensor, the control circuit
configured to be electrically isolated from the first electrical
conductor, and the control circuit configured to be communicatively
coupled to the first electrical conductor when the coupling member
is coupled to the outer jacket.
12. The system of claim 11 wherein the coupling member further
comprises: a base portion; a lid portion; a latch member configured
to couple the lid portion to the base portion; a passage through
the first sensor module defined by the base portion and lid
portion, the passage defining an inside diameter configured to mate
with an outside diameter of the outer jacket; wherein the coupling
member configured to abut the outer jacket of the sensor cable.
13. The system of claim 12 wherein the coupling member is
configured to circumscribe the outer jacket of the sensor
cable.
14. The system of claim 12 wherein the coupling member further
comprises a hinge coupled between the base portion and the lid
portion, the hinge disposed opposite the latch member.
15. The system of claim 11 wherein the first sensor module further
comprises: an interior volume defined by the first sensor module; a
second electrical conductor disposed within the interior volume of
the first sensor module; a magnetic material disposed around the
second electrical conductor within the interior volume of the first
sensor module, the magnetic material configured to direct magnetic
flux created around the second electrical conductor toward first
electrical conductor.
16. The system of claim 11 wherein the first sensor module further
comprises: an interior volume; a second electrical conductor
disposed within the interior volume of the first sensor module; a
magnetic material disposed around the second electrical conductor
within the interior volume of the first sensor module, the magnetic
material configured to direct magnetic field created around the
first electrical conductor toward the second electrical
conductor.
17. The system of claim 11: wherein the sensor cable further
comprises a second electrical conductor disposed within the
interior volume; wherein the first sensor module further comprises:
an interior volume; a third electrical conductor disposed within
the interior volume of the first sensor module; a first magnetic
material disposed around the third electrical conductor within the
interior volume of the first sensor module, the first magnetic
material configured to direct magnetic flux created around the
second electrical conductor toward first electrical conductor; a
fourth electrical conductor disposed within the interior volume of
the first sensor module; and a second magnetic material disposed
around the third electrical conductor within the interior volume of
the first sensor module, the magnetic material configured to direct
magnetic flux created around the second electrical conductor toward
second electrical conductor.
18. The system of claim 11 wherein the control circuit further
comprises: a communication module configured to exchange data
communication with the first electrical conductor; a processor
coupled to the communication module; a memory coupled to the
processor; wherein the memory storing a program that, when executed
by the processor, causes the processor to: begin collecting and
storing data from the sensor upon a first command communicated
along the first electrical conductor and received from the
communication module; and cease collecting data from the sensor
upon a second command communicated along the first electrical
conductor and received from the communication module.
19. The system of claim 11 wherein the control circuit further
comprises: a communication module configured to exchange data
communication with the first electrical conductor; a processor
coupled to the communication module; a memory coupled to the
processor; wherein the memory storing a program that, when executed
by the processor, causes the processor to: receive a time
reference, the time reference communicated along the first
electrical conductor and received from the communication module;
and update a time reference maintained by the control circuit.
20. The system of claim 11 wherein the control circuit further
comprises: a communication module configured to exchange data
communication with the first electrical conductor; a processor
coupled to the communication module; a memory coupled to the
processor; wherein the memory storing a program that, when executed
by the processor, causes the processor to send portions of data
collected from the sensor through the communication module, the
sending along the first electrical conductor.
21. The system of claim 11 further comprising a communication port
coupled to the control circuit, the first sensor module configured
to enable access to the communication port when the sensor module
is in a non-submerged state.
22. The system of claim 11 wherein the sensor comprises at least
one sensor selected from the group consisting of: geophones,
hydrophones, accelerometers, electrodes, magnetometers, and any
combination thereof.
23. A sensor module comprising: a base portion configured to be
releasably coupled to an outer jacket of a sensor cable, the base
portion defining an interior volume; a sensor disposed within the
interior volume; a passage defined, at least in part, by the base
portion, the passage defining an inside diameter configured to mate
with an outside diameter of the outer jacket; and a control circuit
communicatively coupled to the sensor, the control circuit
configured to be electrically isolated from electrical conductors
of the sensor cable, and the control circuit configured to be
communicatively coupled to at least one electrical conductor within
the sensor cable when the base portion is coupled to the outer
jacket.
24. The system of claim 23 further comprising: a lid portion; and a
latch member configured to couple the lid portion to the base
portion; wherein the base portion and lid portion are configured to
circumscribe the outer jacket of the sensor cable.
25. The system of claim 23 wherein the sensor module further
comprising: a first electrical conductor disposed within the
interior volume; a magnetic material disposed around the first
electrical conductor within the interior volume, the magnetic
material configured to direct magnetic flux created around the
first electrical conductor toward an electrical conductor within
the sensor cable.
26. The system of claim 23 wherein further comprising: a first
electrical conductor disposed within the interior volume; a
magnetic material disposed around the first electrical conductor
within the interior volume, the magnetic material configured to
direct magnetic field created around the first electrical conductor
toward an electrical conductor within the sensor cable.
27. The system of claim 23 wherein the control circuit further
comprises: a communication module configured to exchange data
communications with an electrical conductor within the sensor
cable; a processor coupled to the communication module; a memory
coupled to the processor; wherein the memory storing a program
that, when executed by the processor, causes the processor to:
begin collecting and storing data from the sensor upon a first
command communicated along the electrical conductor of the sensor
cable and received from the communication module; and cease
collecting data from the sensor upon a second command communicated
along the electrical conductor of the sensor cable and received
from the communication module.
28. The system of claim 23 wherein the control circuit further
comprises: a communication module configured to exchange data
communication with an electrical conductor within the sensor cable;
a processor coupled to the communication module; a memory coupled
to the processor; wherein the memory storing a program that, when
executed by the processor, causes the processor to: receive a time
reference, the time reference communicated along the electrical
conductor of the sensor cable and received from the communication
module; and update a time reference maintained by the control
circuit.
29. The system of claim 23 wherein the control circuit further
comprises: a communication module configured to exchange data
communication with an electrical conductor of the sensor cable; a
processor coupled to the communication module; a memory coupled to
the processor; wherein the memory storing a program that, when
executed by the processor, causes the processor to send portions of
data collected from the sensor through the communication module,
the sending along the electrical conductor of the sensor cable.
30. The system of claim 23 further comprising a communication port
coupled to the control circuit, the base portion configured to
enable access to the communication port when the sensor module is
in a non-submerged state.
31. The system of claim 23 wherein the sensor comprises at least
one sensor selected from the group consisting of: geophones,
hydrophones, accelerometers, electrodes, magnetometers, and any
combination thereof.
Description
BACKGROUND
[0001] Geophysical surveying is a technique where three-dimensional
geophysical "pictures" of the state of an underground formation are
taken with the use of energy (e.g., acoustic, electromagnetic,
etc.) that penetrates the underground formation. Geophysical
surveying takes place not only on land, but also in marine
environments. Marine-based geophysical surveying faces significant
challenges that are not faced by land-based surveying systems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] For a detailed description of exemplary embodiments,
reference will now be made to the accompanying drawings in
which:
[0003] FIG. 1 shows a perspective cut-away view of a geophysical
survey conducted in a marine environment in accordance with at
least some embodiments;
[0004] FIG. 2 shows a perspective cut-away view of a sensor cable
and attached sensor modules in accordance with at least some
embodiments;
[0005] FIG. 3 shows side elevation, partial cut-away, views of a
sensor module in accordance with at least some embodiments;
[0006] FIG. 4 shows a block diagram of a coupling system between
the sensor cable and a sensor module in accordance with at least
some embodiments;
[0007] FIG. 5 shows a block diagram of a coupling system between
the sensor cable and a sensor module in accordance with at least
some embodiments view;
[0008] FIG. 6 shows a cut-away elevation view of a sensor module in
accordance with at least some embodiments;
[0009] FIG. 7 shows a block diagram of a control circuit of a
sensor module in accordance with at least some embodiments;
[0010] FIG. 8 shows a block diagram of an example system in
accordance with at least some embodiments; and
[0011] FIG. 9 shows a method in accordance with at least some
embodiments.
NOTATION AND NOMENCLATURE
[0012] Certain terms are used throughout the following description
and claims to refer to particular system components. As one skilled
in the art will appreciate, different companies may refer to a
component by different names. This document does not intend to
distinguish between components that differ in name but not
function.
[0013] In the following discussion and in the claims, the terms
"including" and "comprising" are used in an open-ended fashion, and
thus should be interpreted to mean "including, but not limited to .
. . ." Also, the term "couple" or "couples" is intended to mean
either an indirect or direct connection. Thus, if a first device
couples to a second device, that connection may be through a direct
connection or through an indirect connection via other devices and
connections.
[0014] "Releasably coupled" shall mean that a first device
mechanically couples to a second device in such a way that the
first device can be mechanically detached from the second device
without damage to or disassembly of either device or intermediate
devices. Devices coupled such that detachment requires cutting,
breaking, deforming, damaging, or disassembly shall not be
considered to be releasably coupled.
[0015] "Marine environment" shall mean an underwater location
regardless of the salinity of the water. Thus, even an underwater
location in a body of fresh water shall be considered a marine
environment.
[0016] "Sea floor" shall mean the boundary of a body of water and
the underlying sediment or rock. The term sea floor shall not imply
anything regarding the salinity of the water, and thus even the
boundary of a body of fresh water and the underlying sediment or
rock shall be considered a sea floor.
[0017] "On the sea floor" shall mean either in direct contact with,
or no more than about 50 feet above the sea floor.
[0018] "Surface" in relation to the top of a body of water shall
mean any location 100 feet below mean sea level and above.
DETAILED DESCRIPTION
[0019] The following discussion is directed to various embodiments
of the invention. Although one or more of these embodiments may be
preferred, the embodiments disclosed should not be interpreted, or
otherwise used, as limiting the scope of the disclosure or the
claims. In addition, one skilled in the art will understand that
the following description has broad application, and the discussion
of any embodiment is meant only to be exemplary of that embodiment,
and not intended to intimate that the scope of the disclosure or
the claims is limited to that embodiment.
[0020] Various example systems and methods are directed to
geophysical surveying in marine environments where the sensors used
for the geophysical surveying (e.g., geophones, hydrophones,
accelerometers, electrodes, magnetometers) are stationary and are
placed on or near the sea floor. More particularly still, at least
some of the various embodiments are systems where a distance
between sensors along a sensor cable can be selected prior to
deployment. The specification first turns to illustrative systems
to orient the reader, and then to specifics regarding installation
and use of the example systems.
[0021] FIG. 1 shows a perspective cut-away view of a portion of a
marine environment showing deployment of sensors for a marine-based
geophysical survey. In particular, FIG. 1 shows the surface 100 of
the water. At a distance D below the surface 100 resides the sea
floor 102, and below the sea floor 102 resides a subsurface
formation of interest, illustratively a hydrocarbon reservoir 104.
In some locations the precise depth of the sea floor 102 is easily
discernible, such as in locations where the sea floor is defined by
a rock layer. In other locations, the sea floor 102 may be defined
by a layer of silt, sand, mud, and/or organic material that has
increasing density with increase depth, starting from a density
approximately the same as the surrounding water. Thus, the precise
depth where the sea floor 102 begins may be harder to quantify in
some cases.
[0022] Within the example environment of FIG. 1 resides a
stationary vessel 106, illustratively shown as a boat. The example
stationary vessel 106 may remain in place based on one or more
anchors (not specifically shown), or the stationary vessel 106 may
be dynamically positioned to remain at a particular location.
Communicatively coupled to a computer system on the stationary
vessel 106 is a sensor cable 108 that extends from the stationary
vessel 106 to the sea floor 102. In other example system, the
stationary vessel may be a buoy coupled to the sensor cable 108,
and also communicatively coupled to land-based computer (e.g.,
communicatively coupled by satellite or point-to-point wireless
transmission). The sensor cable 108 comprises a plurality of sensor
modules (e.g., sensor modules 110) that are associated with the
sensors appropriate for the geophysical survey, such as
hydrophones, goephones, accelerometers, electrodes, and/or
magnetometers.
[0023] In order to place the sensor cable 108 (and sensor modules
110) on the sea floor 102, a work vessel 112 may hold the sensor
cable on a deployment device 114, illustratively shown as a reel
structure around which the sensor cable 108 may be spooled. The
work vessel 112 may sail away from the stationary vessel 106 while
simultaneously feeding the sensor cable 108 off the deployment
device 114, with the sensor cable 108 ultimately coming to rest on
the sea floor. The example system of FIG. 1 shows sensor cable 108
extending in a straight line away from the stationary vessel 106,
but such is merely an example, the work vessel 112 may lay the
sensor cable in any suitable pattern relative to the location of
the stationary vessel 106. By precise measurement of the location
and speed of the work vessel, and knowledge of the distance between
the sensor modules and the depth of the water, the location of each
sensor module may be accurately determined. In yet still other
example systems, the sensor cable 108 may be deployed by a remotely
operated vehicle (ROV) or an autonomously operated vehicle (AOV)
which deploys the sensor cable 108, and communicates with the
various sensor modules 110.
[0024] Regardless of the precise deployment mechanism, once the
sensor cable 108 (and in some cases other sensor cables not
specifically shown) has been deployed to the sea floor 102, a
geophysical survey may take place by release of energy (e.g., by
way of an air gun, vibrator, antenna, or magnetic coil) within the
water. Measurement of signals that return to the sensor modules
after reflection from one or more features below the sea floor are
recorded by the sensor modules 110, such as reflections of the
acoustic or electromagnetic energy from the hydrocarbon bearing
reservoir 104. After the geophysical survey is complete, the
example sensor cable 108 may be retrieved, either by the work
vessel 114 or by the stationary vessel 106. The system of FIG. 1 is
merely an example to orient the reader. Many variations regarding
deployment of one or more sensor cables to the sea floor are
possible, and thus the example system of FIG. 1 should not be read
to restrict possible deployment scenarios to just the example
system shown.
[0025] There are a host of parameters associated with geophysical
surveys that may be selected and/or adjusted for any particular
situation. For example, the physical location at which the energy
is released may be selected to achieve particular goals for the
geophysical survey. The strength of the energy release may be
adjusted (e.g., the strength of the energy release may be adjusted
as a function of depth of the hydrocarbon bearing formation 104
beneath the sea floor 102). The pattern of the sensor cable 108
along the sea floor 102 may be selected to meet particular needs of
the survey (e.g., expansive pattern for exploratory surveys, and a
dense pattern for determining particular properties about a known
hydrocarbon reservoir). Further still, the spacing "S" between the
sensor modules may be selected to achieve certain goals (e.g.,
surveys of shallow hydrocarbon reservoirs may use close spacing,
while surveys of deep hydrocarbon reservoirs may use extended
spacing).
[0026] In the related-art, the spacing between sensor modules is
controlled by the sensor cable. That is, in the related-art the
overall sensor cable is divided into a plurality of sensor cable
portions, where each sensor cable portion has a connector on each
end. A connector is an electrical and/or optical coupling device
configured for use in marine environments. An overall sensor cable
is constructed by coupling sensor modules in series between sensor
cable portions by way of the connectors. Thus, the overall sensor
cable may be constructed one piece at a time, with the spacing
between modules dictated by the lengths of the sensor cable
portions.
[0027] The related-art sensor cables have limitations and/or
shortcomings. If a different spacing between sensor modules is
desired, a completely different sensor cable (having shorter or
longer sensor cable portion lengths) is used. Moreover, each
connector represents a discontinuity in the outer jacket of the
sensor cable where water encroachment and mechanical failure are
more likely to occur. Moreover, by connecting sensor modules and
sensor cable portions in series, the sensor modules themselves may
carry mechanical load (i.e., tension) during deployment and
retrieval.
[0028] The problems noted above are addressed, at least in part, by
a system where sensor modules may be coupled to a sensor cable at
any location along an extended axial length of the sensor cable
without requiring discontinuities in the outer jacket of the sensor
cable. That is, the sensor modules couple to the sensor cable
without using connectors. FIG. 2 shows a perspective view of a
portion of a geophysical system 200 in accordance with at least
some embodiments. In particular, FIG. 2 shows a sensor cable 108,
as well as two sensor modules 204 and 206. Sensor module 204 is
shown fully coupled to the sensor cable 108, while sensor module
206 is shown partially coupled to the sensor cable 108 to show an
example system.
[0029] The sensor cable 108 comprises an elongated outer jacket
208. The example outer jacket 208 may take any suitable form. In
one example system, the elongated outer jacket 208 is flexible and
constructed of polyurethane, but other water-tight polymeric and
non-magnetic substances may also be used. The outer jacket 208
defines a central axis 210 along the long dimension of the outer
jacket. In some example systems the sensor cable 108 may be several
kilometers in length, and thus the outer jacket 208 may have a
similar length. The outer jacket 208 defines an interior volume
212. Within the interior volume 212 resides one more electrical
conductor, and example systems may comprise two electrical
conductors 214 and 216. As illustrated, the electrical conductors
may be disposed on opposite sides of the interior volume 212, but
such placement is not strictly required. Other devices and/or
components may likewise reside within the interior volume (e.g.,
strength members) as well as devices to enable the relative
placement of the electrical conductors 214 and 216, but the
additional devices are not shown in FIG. 2 so as not to unduly
complicate the figure. The outer jacket also defines an outside
diameter (OD), and where the outside diameter is uniform not only
at the locations where the example sensor modules 204 and 206 are
coupled, but also between the sensor modules and beyond.
[0030] In addition to the electrical conductors 214 and 216 (and
possibly strength members), the interior volume 212 may be filled
with a substantially non-compressible substance such that the
sensor cable 108 retains its shape at depth within the marine
environment. In example systems the interior volume 212 may be
filled with a water- or petroleum-based liquid, or a water- or
petroleum based gel. Inasmuch as the sensor cable is to be deployed
on the sea floor, the sensor cable 108 may be negatively buoyant,
and the substance within the interior volume 212 may thus be
selected to achieve particular buoyancy.
[0031] Still referring to FIG. 2, sensor module 204 is shown
coupled to the sensor cable 108, and in particular coupled such
that the sensor module 204 abuts and circumscribes the outer jacket
208. The example sensor module 204 comprises a base portion 220 and
a lid portion 222. In some cases, the lid portion 222 may couple to
the base portion by a hinge (not visible in FIG. 2) on one side,
and may couple to the base portion 220 by way of a latch 224
disposed opposite the hinge. It is within the base portion 220 that
various devices reside, such as the sensor and a control circuit
coupled to the sensor (discussed more below).
[0032] The sensor module 206 may be of similar design and
construction as sensor module 204. In the view of FIG. 2, however,
sensor module 206 is shown in a configuration where the base
portion 226 abuts the outer jacket 208, but where the lid portion
228 is in an open configuration. Mechanically coupling a sensor
module (such as sensor module 206) may thus involve opening the lid
portion 228 with respect to the base portion 226. While in the open
configuration the base portion 226 (or, alternatively, the lid
portion 228) may be placed in an abutting relationship with the
outer jacket 208. Once the sensor module is at the desired axial
location, the lid portion 228 may be closed and the latch 230
latched to the base portion 226. It is noted that while latch 230
is shown coupled to the lid portion, the latch 230 may also couple
to the base portion, or the latch may comprises multiple components
distributed among the lid portion 228 and the base portion 226.
Furthermore, multiple latches may be used.
[0033] In accordance with example systems, a sensor module may be
placed at substantially any location along the sensor cable 108. In
the section of the sensor cable shown in FIG. 2, for example, the
sensor modules may be placed at any location, and thus the spacing
S may be set or adjusted for any particular geophysical survey
without the need to obtain a different sensor cable 108. Moreover,
the outer jacket 208 may be continuous for long distances in axial
length (stated otherwise, a plurality of sensor modules may be
placed over a continuous length of outer jacket), thus eliminating
the need for connectors. Moreover, to the extent axial forces are
carried along the sensor cable 108 (e.g., during deployment, during
retrieval), the axial forces are not carried by the sensor modules,
which may make the design and construction of the sensor modules
cheaper and less expensive than sensor modules that must carry
axial load imposed upon the sensor cable.
[0034] FIG. 3 shows a side elevation view of two separate sensor
modules in accordance with further example systems. In particular,
the left sensor module 300 comprises a base portion 302 and the lid
portion 304, where the lid portion 304 is shown coupled to the base
portion 302 by way of a hinge 303. In some situations, the base
portion 302 and lid portion 304 may be referred to as a coupling
member. The lid portion 304 and base portion 302 define a passage
306 through the sensor module, where the passage 306 defines an
inside diameter configured to abut and circumscribe the outside
diameter of a sensor cable (not shown in FIG. 3). The base portion
302 and lid portion 304 may be constructed of any suitable
material, such as plastic material, metallic materials, and
combinations. In accordance with example systems, the base portion
302 defines an interior volume 308 (shown in partial cutaway)
within which various electrical components may reside, the
electrical components discussed more below.
[0035] The right sensor module 310 of the FIG. 3 shows that, in
other example systems, rather than the lid portion 312 being hinged
to the base portion 314, the lid portion may be fully separable
from the base portion 314. In these example systems, latches 316
and 318 on opposite sides of the lid portion 312, on opposite sides
of the base portion 314, or both, may be used to couple the sensor
module to the sensor cable at the desired axial location along the
sensor cable 108.
[0036] The specification now turns to a discussion of the
communicative coupling between the sensor modules (e.g., 110, 204,
206, 300, 310) and the electrical conductors (e.g., 214, 216)
within the sensor cable 108. In the various example systems, the
sensor modules may be placed at substantially any location along
the sensor cable 108, and as described the outer jacket 208 may be
continuous in the regions where the sensor modules connect. Thus,
in the example systems control circuits and sensors within the
sensor modules are electrically isolated from the electrical
conductors disposed within the outer jacket 208 of the sensor cable
108. Nevertheless, the control circuits are communicatively coupled
to one or more of the electrical conductors. More particularly, in
example systems, each control circuit within each sensor module may
be inductively coupled to the one or more of the electrical
conductors 214 and 216 within the outer jacket 208 such that the
control circuit can receive communications from a computer system
controlling the geophysical survey.
[0037] FIG. 4 shows an electrical block diagram of an example
system comprising a sensor module communicatively coupled to a
sensor cable. In particular, FIG. 4 shows system 400 comprising a
surface computer 402 communicatively coupled to the electrical
conductors 214 and 216 of a sensor cable 108. In spite of the fact
FIG. 4 is an electrical block diagram, in order to convey certain
concepts the outer jacket 208 of the sensor cable 208 is shown in
dashed lines. Thus, the electrical conductors 214 and 216 reside
within the outer jacket 208, and are electrically coupled to the
surface computer 402. FIG. 4 also shows various components
associated with an example sensor module. In particular, FIG. 4
shows a control circuit 404 coupled to sensor 406. The sensor 406
is one or more sensors suitable for use in geophysical surveying.
In one example system the sensor 406 is a hydrophone, which senses
acoustic energy incident upon the sensor. In another example system
the sensor 406 is a geophone, which senses movement (displacement)
associated with acoustic energy incident upon the sensor. In yet
still further example systems, the sensor 406 may be one or more
accelerometers (e.g., a three-axis accelerometer), which sensor(s)
sense acceleration associated with acoustic energy incident upon
the sensor(s). In other example systems, the sensor 406 may be an
electrode or magnetometer, which senses electromagnetic field
amplitude and/or phase incident upon the sensor. In yet still other
cases, a combination of two or more different types of sensors may
be included in the sensors 406.
[0038] The one or more sensors 406 are communicatively coupled to
the control circuit 404. In the example systems, the control
circuit 404, upon command from the surface computer 402, reads data
created by the sensor 406 and stores the data for later download.
The control circuit 404 may also cease data collection upon the
command of the surface computer 402, and further the control
circuit may send portions or all the data to the surface computer
over the sensor cable 108. For example, the control circuit 404
(discussed in greater detail below) may store the data collected by
sensor 406 for download to the surface computer 402 (or some other
computer system) once the sensor module within which the control
circuit 404 is disposed has been retrieved to the surface. However,
small portions of the data (sometimes referred to quality control
(QC) data) may be sent to the surface computer 402 by the control
circuit 404 during periods of time when the sensor module is
located on the sea floor.
[0039] In the various example systems, the control circuit 404
communicates with the surface computer 402 over the one or more
electrical conductors disposed within the sensor cable 108. More
particularly, in the example systems the control circuit 404 and
the computer system 402 are communicatively coupled in spite of the
fact that the control circuit 404 is electrically isolated from the
electrical conductors 214 and 216 by at least the outer jacket 208,
the outer cover of the base portion, and in many cases insulation
covering the electrical conductors 214 and 216 themselves. In the
system of FIG. 4, the control circuit is coupled to an electrical
conductor 410 that is located within the base portion of the sensor
module, and arranged in such a way that the electrical conductor
runs parallel to the at least one of the electrical conductors. As
illustrated, in some cases the electrical conductor is arranged to
extend parallel both to the electrical conductor 214 and the
electrical conductor 216. The communicative coupling in the example
systems is an inductive coupling system.
[0040] Inductive coupling is based, at least in part, on magnetic
fields that surround a conductor in the presence of electrical
current flow along the conductor. In particular, considering
traditional electrical current flow (i.e., hole flow, with actual
electron flow in the opposite direction), a magnetic field is
created around an electrical conductor as characterized by the
"right hand rule" (where the thumb indicates the direction of
current flow, and the finger movement from an open-hand position to
a closed-hand represented the direction of the magnetic field).
Thus, electrical current flow along the conductor 410 in the
direction indicated by arrow 412 produces a magnetic field. The
magnetic field produced by the electrical current flow extends
outward from the conductor 410. In the various embodiments, the
electrical conductor 410 is positioned within sensor module such
that the conductor is physically close (e.g., within 5 centimeters
(cm), and in some cases within 2 cm) to an electrical conductor
within the sensor cable 108. The proximity of the electrical
conductor 410 to an electrical conductor within the sensor cable
108 enables the magnetic field created responsive to current flow
in the conductor 410 to at least partially encompass the portion of
the electrical conductor within the sensor cable 108 parallel to
the conductor 410. In the example system of FIG. 4, portion 414 of
electrical conductor 216 is parallel to the corresponding portion
of electrical conductor 410, and thus the magnetic field created by
electrical current flow in conductor 410 at least partially
encompasses the portion 414 of electrical conductor 216.
[0041] A second aspect of the inductive coupling may comprise the
phenomenon that an electrical current can be induced in an
electrical conductor when the electrical conductor is exposed to a
time varying magnetic field. Thus, in accordance with the example
systems, communicative coupling from the control circuit 404 to the
surface computer 402 may take place by a creation of time varying
electrical current flow in the electrical conductor 410. The time
varying electrical current flow thus creates a time varying
magnetic field around the conductor, and because the portion 414 of
the electrical conductor 216 is exposed to the time varying
magnetic field, electrical currents are induced in the electrical
conductor 216 proportional to the current flow in the conductor
410. The opposite is also true. That is, communicative coupling
from the surface computer 402 to the control circuit 404 may take
place by a creation of time varying electrical current flow in the
electrical conductor 216 creating a time varying magnetic field
around the conductor. Because the electrical conductor 410 is
exposed to the time varying magnetic field, electrical currents are
induced in the electrical conductor 410 proportional to the current
flow in the conductor 216. Thus, two-way data communication may
take place between the surface computer 402 and the control circuit
404 in spite of the fact that the control circuit 404 and computer
system 402 are electrically isolated from one another.
[0042] The example system of FIG. 4 shows what may be referred to
as a differential signaling system. That is, time varying
electrical current flow (such as electrical current illustrated by
line 412) in the electrical conductor 410 induces a corresponding
current in the portion 414 of the electrical conductor 216. As the
same current flows in the electrical conductor 410 proximate to
portion 416 of the electrical conductor 214, an opposite current
flow is induced in the electrical conductor 214. Thus,
communicative signals from the control circuit 404 to the surface
computer system 402 may be detected by sensing differences in
current and/or voltages between the electrical conductors 214 and
216. Likewise, communicative signals from the surface computer 402
to the control circuit 404 may sent by inducing differential
current and/or voltages between the electrical conductors 214 and
216. However, use of a differential signaling is only an example,
and other systems are possible.
[0043] FIG. 5 shows an electrical block diagram of an alternate
system of communicatively coupling the control circuit 404 to the
electrical conductors 214 and 216. In particular, the system 500 of
FIG. 5 comprises the control circuit 404, electrical conductor 502
(which runs parallel and proximate to the electrical conductor
216), as well as electrical conductor 504 (which runs parallel and
proximate to the electrical conductor 214). Thus, in the example
system the control circuit 404 may send and receive data
communications over electrical conductor 216 by way of inductive
coupling, and likewise send and receive data communications over
electrical conductor 214 by way of inductive coupling. The
communications over electrical conductor 214 need not be same, or
even related to, the communications over electrical conductor 216.
For example, the control circuit may send messages to the surface
computer (not shown in FIG. 5) over the inductive coupling with the
electrical conductor 216, and the control circuit may receive
messages from the surface computer over the inductive coupling with
electrical conductor 214. Further still, even if the sensor cable
has two (or more) electrical conductors, it is not strictly
required that the control circuit 404 be communicatively coupled to
all the conductors in the sensor cable. For example, a sensor
module may be arranged and constructed to be communicatively
coupled to only one (or a small subset of) the electrical
conductors within the sensor cable, such that one or dedicated
groups of sensor modules are dedicate to particular communication
pathways within the sensor cable.
[0044] Returning to FIG. 4, in some example systems having the
electrical conductor 410 placed parallel to a portion of one or
more electrical conductors within the sensor cable 108 may be
sufficient to provide communicative coupling between the control
circuit 404 and the surface computer system 402. However, in order
to increase the coupling efficiency between the electrical
conductors in the sensor module and electrical conductors within
the sensor cable 108, in other example systems the electrical
conductor 410 may be associated with one or more sets of magnetic
material. In FIG. 4, the system 400 comprises a magnetic material
420 associated with electrical conductor 410 and portion 414 of the
electrical conductor 216, and system 400 also comprises a magnetic
material 422 associated with electrical conductor 410 and portion
416 of the electrical conductor 214. The sets of magnetic material
may be any low reluctance material current available (e.g., stacks
of thin sheets of metallic material such as used in the stators of
electrical motors) or later-developed.
[0045] In non-magnetic media (such as air, plastics, free space),
the magnetic field associated with electrical current flow in the
electrical conductor 410 expands out a certain distance from the
electrical conductor 410 (as a function of the field strength).
However, in the presence of a magnetic material, the magnetic field
attempts to confine itself to be predominantly within the magnetic
material (again, as a function of field strength). In the example
system of FIG. 4, and referring to magnetic material 420 for
purposes of explanation, the electrical conductor 410 is situated
such that the magnetic material 420 is disposed around the
conductor 410. In some example systems, the electrical conductor
may run through an aperture defined in the magnetic material 420.
Of course, the magnetic material 420 is confined to the sensor
module outer cover (e.g., the base portion). In regions where the
magnetic material is present, the magnetic field created by
electrical current flow within the electrical conductor 410 will
tend to confine itself within the magnetic material, but then will
expand out in regions lacking the magnetic material (i.e., the
direction of the portion 414 of the electrical conductor 216).
Thus, the magnetic material tends to focus or direct the magnetic
field toward the portion 414 of the electrical conductor 216. The
focusing or directing of the magnetic field increasing the
inductive coupling between the conductor 410 and the portion 414 of
the conductor 216. The focusing effect of the magnetic material 420
is likewise present in data communications from the surface
computer system 402 along the electrical conductors within the
sensor cable 108.
[0046] FIG. 6 shows a cross-sectional elevation view of the sensor
cable and a sensor module, the view taken substantially along lines
6-6 of FIG. 2. In particular, FIG. 6 shows the example sensor
module 204 comprising the base portion 220 and lid portion 222. In
the example sensor module, the lid portion 222 couples to the base
portion 220 by way of a hinge member 600 (where the axis of
rotation about the hinge member 600 is perpendicular to the plane
of the page). The base portion 220 defines an interior volume 602.
Within the interior volume 602 are the control circuit 404, sensor
406, and electrical conductor 410. Also visible in FIG. 6 are
cross-sectional views of the magnetic materials 420 and 422
disposed within the interior volume 602. In the example system, the
electrical conductor 410 extends through apertures in the magnetic
materials 420 and 422, such as aperture 604 associated with
magnetic material 422. As discussed above, the magnetic materials
420 and 422 act to focus the magnetic fields created by the
electrical conductor 410 toward respective electrical conductors
216 and 214. Likewise, the magnetic materials 420 and 422 focus
magnetic fields created by the conductors 214 and 216 toward the
electrical conductor 410.
[0047] The specification now turns to an example electrical system
which may be implemented within a sensor module. FIG. 7 shows an
electrical block diagram of a control circuit of a sensor module in
accordance with at least some embodiments. In particular, FIG. 7
shows that, in example systems, the control circuit 404 can be
logically divided into a communication module 700, power module
740, a computer system 702, and a battery 704. Each will be
discussed in turn, starting with the battery 704.
[0048] Battery 704 may be any suitable rechargeable battery or
battery system configured to provide operational power to the other
components of the control circuit 404, as well as to power the one
or more sensors (the sensors not specifically shown in FIG. 7). In
some cases, the battery 704 may power the various electrical
components for extended periods of time (e.g., a month or more)
during periods of time when a sensor module remains on the sea
floor. That is, in cases where no power can be provided over the
sensor cable 108, the battery 704 may provide operational power for
multiple geophysical surveys taken over days or weeks. In other
cases, the battery 704 may be charged by power extracted from the
sensor cable, as illustrated by the electrical connection 706
between the power module 740 and the battery 704. The various
electrical connections between the battery 704 and the other
control circuit 404 devices which derive operational power from the
battery 704 are not shown so as not to unduly complicate the
figure.
[0049] The example control circuit 404 further comprises the
communication module 700. As the name implies, the communication
module 700 may be an interface between the computer system 702 and
the electrical conductors of the sensor cable over which messages
are exchanged with the surface computer. In the example system, and
considering first messages received by the control circuit over the
electrical conductor 410, the electrical conductor 410
illustratively couples to a high pass filter 710. The high pass
filter may filter lower frequency signals (such as signals used to
provide charge to the battery, discussed more below). The high pass
filter 710 may implement other electrical features, such as
impedance matching and signal amplification. The resultant signal
from the high pass filter 710 couples to a communication circuit
712. The communication circuit 712 performs demodulation and/or
decoding of the signals received over the sensor cable 108. The
precise internal electrical structure of the communication module
is dependent upon the type of modulation and communication system
implemented across the sensor cable. For example, in some systems
the modulation system may be an amplitude shift keying system where
binary states are encoded in different amplitudes of a carrier
frequency (e.g., off as one state, and on as a second state). In
yet still other cases, the modulation system may be a frequency
shift keying system wherein binary states are encoded in different
frequencies (e.g., a first frequency representing a first binary
state, and a second frequency representing a second binary state).
Further still, example systems may use quadrature amplitude
modulation (QAM) where the electrical conductors of the sensor
cable simultaneously carry signals of different frequency, and
wherein various possible states are encoded in the relationship of
the two simultaneous signals. Regardless of the modulation system
used, messages sent from the surface computer to the sensor module
are demodulated and decoded by the communication circuit 712 and
passed to the computer system 702.
[0050] Various types of messages may be sent from the surface
computer to the computer system 702. For example, the surface
computer may send a message for the computer system 702 to begin
recording data from an attached sensor associated with the
geophysical survey. Likewise, at some later time the surface
computer may send a message to the sensor module to cease the
collection of data from the attached sensor. Other example messages
include time references.
[0051] With regard to time references, each sensor module 404
maintains a highly accurate time reference. In many cases the time
reference is maintained by the computer system 702 responsive to a
highly accurate crystal oscillator (not specifically shown). In
order for geophysical data collected by all the sensor modules to
be analyzed to identify parameters of an underground formation, a
precise arrival time of the acoustic energy at each sensor module
is noted. In order to initially align the time references across
all the sensor modules coupled to a sensor cable, the surface
computer may send one or more messages that include a time
reference. The computer system 702 may thus receive a message with
a time reference, and update the time reference of the control
circuit 404 consistent with the message. Moreover, in some cases
the sensor modules may remain on the sea floor for extended periods
of time (e.g., a month or more), and thus even if each sensor
module comprises a highly accurate time reference, over extended
periods of time drift regarding current time may occur as between
sensor modules. Again, the surface computer may address such issues
by sending time references to the sensor modules (e.g., a broadcast
message), and wherein each sensor module receives the message and
corrects the current time to better align the time perceived by
each sensor module.
[0052] Still referring to FIG. 7, the direction of message flow is
not limited to just messages from the surface computer to the
sensor module. In some systems, the control circuit 404, and in
particular the communication module 700, may send messages to the
surface computer over the sensor cable. The message range from
acknowledgment messages (e.g., acknowledging a command to begin
recording) to large messages with data payload directed to the
surface computer. Consider, as an example, that the control circuit
404 in FIG. 7 has stored therein a large quantity of sensor data
recorded during a geophysical survey operation. In some example
systems, during the geophysical survey, after the geophysical
survey, or both, the control circuit 404 may send the data to the
surface computer over the sensor cable using any suitable
modulation scheme. In some cases, all the data recorded by the
control circuit 404 may be sent to the surface, while in other
cases only a small portion may be sent for quality control purposes
(i.e., QC data).
[0053] Turning now to the computer system 702 of the example
control circuit 404. In some cases, the computer system 702
comprises processor 720 coupled to a memory 722. The processor 720
may be any currently available or after developed processor. The
memory 722 may be the working memory for the processor 720, and
from which instructions are executed. In some systems, the memory
is an array of random access memory (RAM) devices. While in some
systems the processor 720 and memory 722 may be individual
components operatively coupled together, in one example system the
processor 720 and memory 722 are an integrated component in the
form of a low power microcontroller. The processor 720 may further
couple to a long-term storage device 724. Storage device 724 may
comprise any suitable long term non-volatile storage device or
devices, such as an array of battery-backed RAM, or one or more
flash memory devices. In example systems, the storage device 724
may be the location that stores instructions that enable the
computer system 702, and thus the control electronics 404, to act
as a sensor module in a geophysical survey system. Further, the
storage device 724 may be the location within which sensor data
recorded during a geophysical survey is stored until the data can
be sent to the surface over the geophysical cable, and/or
"downloaded" once the sensor module is retrieved to the
surface.
[0054] In cases where sensor data is held within a sensor module
until the sensor module is brought back to the surface, the control
electronics 404 may further comprise a communication port 730
communicatively coupled to the computer system 702. In the
non-submerged state, the communication port 730 may be accessible
(e.g., by removal of one or more sealed access panels) so as to
perform various tasks, such as downloading recorded sensor data
from the storage device 724 and updating the computer system 702
software or firmware. The physical and electrical protocol
implemented by the communication port 730 may take any suitable
form, such as a Universal Serial Bus (USB) port or IEEE 1391
"FireWire" system.
[0055] Still referring to FIG. 7, in some example systems the
battery 704 has sufficient energy storage capacity to power a
sensor module over the course of one or more geophysical surveys.
However, in other cases the battery 704 may need to be charged, or
at least the charge supplemented, during periods of time when the
sensor module is submerged. Thus, in accordance with other example
systems, the control circuit 400 further comprises a power module
740. As the name implies, the power module 740 is designed and
constructed to draw power from the sensor cable, and use the power
to charge the battery 704. In one example system, the power module
740 comprises a low pass filter 742. For example, a power signal
may be carried on the electrical conductors 214 and 216, with the
power signal having a first frequency, while the data
communications (either to or from the sensor module) may be encoded
on signals having higher frequency or frequencies. The low pass
filter 742 may thus extract the lower frequency signals induced on
the conductor 410, and may provide other electrical properties,
such as impedance matching. The example power signal that passes
the low pass filter 742 may then be applied to a rectifier circuit
744, which converts the time varying current (i.e., alternating
current (AC)) into a direct current (DC) signal. The DC signal
produced by the rectifier circuit may then be applied to the power
control circuit 746. The power control circuit 746 may provide any
suitable adjustment or control to the power flow, such as voltage
regulation, current flow control, and charge control (e.g., for
automatic charge cut off).
[0056] The various embodiments discussed to this point have assumed
a sensor cable with two electrical conductors, and that
communications with all the sensor modules could be achieved over
two electrical conductors. In some example systems, two conductors
are sufficient (e.g., shorter sensor cables, or sensor cables to
which a smaller number of sensor modules are attached). In other
cases, however, the length of the sensor cable and/or the number of
sensor modules coupled to the sensor cable may make communicating
with each sensor module difficult. In some cases, additional
electrical conductors within the outer jacket 208 may be included,
with the sensor modules either designed to communicate with
specific conductors within the sensor cable, or the radial position
of the sensor modules adjusted such that each sensor module
communicates with a specific electrical conductor or set of
electrical conductors. In other cases, however, sensor cable is
logically divided into smaller communication regions, where each
region may have a plurality of sensor modules, and where a
wide-band backbone communication system communicates with each
logical region.
[0057] FIG. 8 shows, in block diagram form, an example system where
the sensor cable is divided into logical regions. In particular,
FIG. 8 shows a sensor cable 108 comprising the outer jacket 208
(the outer jacket shown in dashed lines). The sensor cable 108 is
logically divided into a plurality of communication regions 800,
802, and 804. Within each communication region resides a plurality
of electrical conductors. For example, within region 800 resides
electrical conductors 806 and 808. Within region 802 resides
electrical conductors 810 and 812. Finally, within region 804
resides electrical conductors 814 and 816. Thus, sensor cable
portions discussed to this point (e.g., FIG. 2) could be a region
within an overall sensor cable.
[0058] In addition to the electrical conductors within each region,
the sensor cable 108 in FIG. 8 further comprises one or more
electrical power conductors 820, and one or more back-bone
communication channels 822. In one example embodiment, the
back-bone communication channel 822 is one or more fiber optic
cables, coaxial cable or cables, one more twisted pairs, or
combinations thereof. As the name implies, the back-bone
communication channel 822 in the example embodiments is main
communication pathway to and from the surface computer 402. Each
communication region extracts message traffic from the back-bone
communication channel 822, and injects message traffic onto the
back-bone communication channel 822 by way of a respective
interface device. For example, interface device 830 may draw
operational power from the electrical power conductors 820, and may
provide the operational power on the conductors 806 and 808 to
power the attached sensor modules 832, 834, and 836. The interface
device 830 may extract message traffic from the back-bone
communication channel destined for the sensor modules in the
communication region 800, and may inject message traffic onto the
back-bone communication channel 822 from the sensor modules in the
communication region 800. Similarly, interface device 840 may draw
operational power from the electrical power conductors 820, and may
provide the operational power on the conductors 810 and 812 to
power the attached sensor modules 842, 844, and 846. The interface
device 840 may extract message traffic the back-bone communication
channel destined for the sensor modules in the communication region
802, and may inject message traffic onto the back-bone
communication channel 822 from the sensor modules in the
communication region 802. Similarly, interface device 840 may draw
operational power from the electrical power conductors 820, and may
provide the operational power on the conductors 810 and 812 to
power the attached sensor modules 842, 844, and 846. Finally,
interface device 850 may draw operational power from the electrical
power conductors 820, and may provide the operational power on the
conductors 814 and 816 to power the attached sensor modules 852,
854, and 856. The interface device 850 may extract message traffic
the back-bone communication pathway channel for the sensor modules
in the communication region 802, and may inject message traffic
onto the back-bone communication channel 822 from the sensor
modules in the communication region 802.
[0059] Referring to communication region 800 as illustrative of all
the communication regions, the interface device 830 may communicate
on the back-bone communication channel using the communication
protocol of the back-bone communication channel 822. For example,
in situations where the back-bone communication channel 822 is a
fiber optical channel, the surface computer and the interface
devices may communication a synchronous optical networking (SONET)
protocol. In yet still other example cases, the back-bone
communication channel 822 may be dedicated point-to-point system
(i.e., computer system 402 to each interface device 830, 840, and
850 over separate channels). In one example system, the separate
channels may each be an Ethernet protocol systems over copper.
[0060] Regardless of the type of physical system and protocol
implement on the back-bone communication channel 822, the interface
device 830 may provide protocol translation and message packet
transfers to and from the sensor modules within the example
communication region 800. On the electrical conductor 806 and 808
side, any suitable communication system and protocol may be used.
For example, the communications between the interface device 830
and the sensor modules 832, 834, and 836 may implement a modified
token ring network, where each sensor module communicates only when
the sensor modules receives the virtual token granting broadcast
permission. In other cases, a time-division multiplexing scheme may
be used to assign time windows within which each sensor module may
broadcast messages.
[0061] Regardless of the precise protocol, logically dividing the
sensor cable into communications regions may facilitate better
two-way communications between the surface computer 402 and the
sensor modules. It is noted that the example interface devices 830,
840, and 850 may be physically too large to reside within the outer
jacket 208 in some cases. Thus, in some example systems, the
interface devices may be coupled within the sensor cable 108
periodically (e.g., one every kilometer) by way of wet-connectors,
thus establishing each communication region.
[0062] FIG. 9 shows a method in accordance with at least some
embodiments. In particular, the method starts (block 900) and
comprises attaching a first sensor module to a sensor cable having
an outer jacket, the first sensor module electrically isolated from
an electrical conductor disposed within the outer jacket of the
sensor cable (block 902). For example, the attaching may comprise
attaching a sensor module such as shown in FIG. 2 to the sensor
cable by a "clam-shell" mechanism. The method may then include
attaching a second sensor module to the sensor cable, the second
sensor module electrically isolated from an electrical conductor
disposed within the outer jacket of the sensor cable (block 904).
Either after attaching the various sensor modules, or
contemporaneously with the attaching of the sensor modules, the
method may include placing the sensor cable and the sensor modules
onto a sea floor (block 906). For example, after a sensor module is
attached on the deck of the work vessel 112, the sensor cable 108
may be fed into the water. Thereafter, the method may comprise:
communicating with the sensor modules by way of the electrical
conductor disposed within the outer jacket (block 908); collecting
geophysical data by the first and second sensor modules while the
sensor cable is on the sea floor (block 910); and downloading to a
computer system geophysical data from the first and second sensor
modules (block 912). The downloading may take place while the
sensor modules are on the sea floor (e.g., over the electrical
conductors of the sensor cable), or the downloading may take place
once each sensor module is brought back to the surface (e.g.,
through the communication port 730). Thereafter the method ends
(block 912), in some cases to be restarted at the next geophysical
survey.
[0063] References to "one embodiment", "an embodiment", "a
particular embodiment", and "some embodiments" indicate that a
particular element or characteristic is included in at least one
embodiment of the invention. Although the phrases "in one
embodiment", "an embodiment", "a particular embodiment", and "some
embodiments" may appear in various places, these do not necessarily
refer to the same embodiment.
[0064] The above discussion is meant to be illustrative of the
principles and various embodiments of the present invention.
Numerous variations and modifications will become apparent to those
skilled in the art once the above disclosure is fully appreciated.
For example, in cases where only a single conductor is disposed
within the sensor cable 108, the water outside the sensor cable may
be used as a return path for electrical current. It is intended
that the following claims be interpreted to embrace all such
variations and modifications.
* * * * *